(a) For projects where supplemental water is available, and you request and receive supplemental water, your assessment will include two components: a base rate, which is for your per-acre water duty delivered to your farm unit; and a supplemental water rate, which is for water delivered to your farm unit in addition to your per-acre water duty.

(b) We publish base and supplemental water rates annually in the Federal Register. The base and supplemental water rates are established to recover the costs identified in section 171.500(a) of this subpart.

(c) If your project has established a supplemental water rate, and you request and receive supplemental water, we will calculate your total annual operation and maintenance assessment by adding the following two totals:

(1) The total assessable acres of your land within the service area of our irrigation facility multiplied by the annual operation and maintenance assessment rate we establish for that facility; and

(2) The actual quantity of supplemental water you request and we agree to deliver (in acre-feet) times the supplemental water rate established for that facility.